1. Field of the Invention
The invention relates to a method for forming via holes of semiconductor devices, and more particularly, to a method for forming a via hole in multiple metal layers, in which a metal barrier layer is formed beneath a photoresistive layer for protecting undesired polymer residue remaining on the bottom and sidewall of a via hole.
2. Related Art
Generally, in VLSI chips, as the density of unit cell of the semiconductor memory device increase, the unit area required for forming the unit memory cell decreases. Accordingly, a multi-layer wiring technique is very important to manufacture a semiconductor memory device. Especially in multi-level wiring process for submicron, the planar topography of metal layers and stabilized resistance of metal via hole are required.
However, when the via hole is formed to expose the metal layer, for example, aluminum metal by the plasma etching method, a portion of the photoresistive layer used as a pattern mask remains on the surface of aluminum metal or side wall of the via hole during the etching process, to thereby form an undesired thin polymer by the sputtering effect. Next, after the completion of the photoresistive removal process or after organic solation removal process, the above mentioned polymer will remain.
Accordingly, the remaining polymer causes the topology and high resistance of via hole, thereby deteriorating the reliability of semiconductor device by not causing any contact between upper metal layer and lower metal layer.
Therefore, the object of the present invention is to provide a method for forming a via hole in multiple metal layers of the semiconductor device, in which a barrier layer as a diffusion protect metal which is formed beneath the photoresistive layer to thereby protect the formation of the polymer of the photoresistive layer when a via hole is formed.
The preceding objects should be construed as merely presenting a few of the more pertinent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to both the summary of the invention and the detailed description, below, which describe the preferred embodiment in addition to the scope of the invention defined by the claims considered in conjunction with the accompanying drawings.